’

20 m

5 m

1 m

Fig. 1b. All Predators. Fig. 1c. Predator Exclusion.

Suppression of soybean aphid and movement of natural enemies in agricultural landscapes in Manitoba

K.G.L. Ishan Samaranayake and Alejandro C. CostamagnaDepartment of Entomology, Faculty of Agricultural and Food Sciences, University of Manitoba, Canada.

Introduction

Results

Conclusions

References

Materials and Methods• The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a major

invasive pest in North America, causing yield losses that can reach $2.4 billion annually in the north-central region of the United States if left untreated (Tilmon et al. 2011).

• In Manitoba, it was first detected in 2001 and large outbreak populations were observed in 2006 and 2008, and minor outbreaks in 2010 and 2011 (Gavloski and Bisht, 2014).

• Generalist natural enemies have shown strong suppression of soybean aphid (Fox et al., 2004; Costamagna et al. 2006).

• Transient generalist predators have ability to track aphid population in multiple crop fields and use different crop and non-crop habitats to gain alternative preys, over wintering sites and protection from disturbances (Sutherland et al. 2001, Tscharntke et al. 2007;).

• Biological control of soybean aphid varies due to the landscape complexity in the Midwest USA (Gardiner et al. 2009).

• The sources of generalist predators in agricultural landscapes have not been studied directly.

Objectives

1) Can natural enemies suppress the soybean aphid populations in different agricultural landscapes in Manitoba?

2) What are the sources of aphidophagous transient generalist predators in the agricultural landscape?

• Soybean aphid populations (14 initial aphids / pot) were manipulated on potted soybean plants (2 plants / pot) in soybean fields (Fig. 1).

• Two treatments: 1) Ambient levels of predators (completely open plants)

(Fig. 1b) 2) Predator exclusion (completely caged plants) (Fig. 1c)

• Each treatment was replicated 5 times / field, in 12 soybean fields in 2013 and 15 soybean fields in 2014 (Fig 1a).

• Total of 120 experimental aphid populations were studied in 2013 and 150 in 2014. • Field sites were selected from high to low landscape complexity with larger to

smaller areas with alfalfa and natural vegetation as sources of aphidophagous natural enemies (Schmidt et al. 2007; Ragsdale et al. 2011).

• Soybean aphids were counted once a week for 2 weeks and predators were quantified weekly in each field with 5 samples of 25 sweeps / sample.

• Aphid numbers were analyzed with split-plot ANOVA with field as a whole plot factor, predator manipulation (treatments) as a subplot factor and week as a repeated measures factor. Separate analyses were conducted for 2013 and 2014.

1) Cage Experiment

2) b. Natural enemy movements • 14 Bidirectional Malaise Traps were established in the border

between soybeans and neighbouring habitats (5 natural vegetation, 4 alfalfa, 3 canola, 1 grass, and 1 wheat borders). 17 field borders were sampled in 2014, but samples are still in process.

• Samples were collected for 3 weeks in 2013.• Directions of the movement of aphidophagous transient natural

enemies between soybean and neighbouring fields were monitored.

• Immigration and emigration of natural enemies in every soybean fields were analyzed with paired t-tests and Wilcoxon paired t-test.

• Neighboring soybean and alfalfa fields were used with similar plant heights (2013 in Gimli and 2014 in Carman).

• 654 Seven-spotted ladybeetles, Coccinella septempunctata L. (Fig. 2) in 2013, and 600 in 2014, were marked with paint markers following van der Werf et al. (2000).

• Beetles were released in six releasing points and recaptured using 5 sweeps / recapture point in 2 hour intervals for 2 consecutive days (2 , 4 , 6 , 8 , 24 , 26, 28 , 30 , 32 and 48 hours after releasing) (Fig. 2).

• Recapture points: 504 in 2013 and 714 points in 2014 (Transect length was increased up to 104 m).• 6 Bidirectional Malaise Traps (BMT, Fig. 3) in 2013 (Fig. 2), and 10 BMT in 2014 in the field border. BMT had

separate collecting jars for each side of the border (Fig. 3).• Lady beetle movements, speed and distance traveled were analyzed with Kruskal -Wallis tests followed by

Sequential Bonferroni corrections; One –way ANOVA models used for BMT data.

2) a. Mark-release recapture experiments of natural enemy movements between soybean and alfalfa

Fig. 5. Suppression of soybean aphids during the 2nd week in 2014.

Fig. 7. Natural enemy movements between soybean and neighbouring habitats, combining all natural enemies (A); and by natural enemy group in natural vegetation (B), in alfalfa (C), in canola (D), and in all field borders combined (E).

Fig. 4. Suppression of soybean aphids in all field in 2013 & 2014.

1) Cage Experiment 2) a. Natural enemy movements, distance and speed: Mark-release recapture

• 36 beetles (5.5 %) recaptured in 2013; 34 (5.6 %) in 2014.• There was a trend of more beetles moving from soybean to alfalfa,

faster and for longer distances(Fig. 6). • This was most likely related to abundant aphids present in alfalfa

fields (2.3 ± 0.4 aphids/25 sweeps [2013], 8.4 ± 0.2[2014] and none on soybeans during our experiments.

• However, movement in both directions suggest alfalfa may act as a good source of natural enemies when the soybean fields are infested.

Fig. 6. C. septempunctata movements within and between soybean (sb) and alfalfa (alf) fields. Number of beetles captured in 1) sweep net samples in 2013 (A) and in 2014 (B); 2) bidirectional malaise trap samples in 2013 (C) and in 2014 (D). Distance travelled by recaptured beetles within and between fields in 2013 (E) and in 2014 (F); and their speed in 2013 (G) and in 2014 (F).

Acknowledgments

2) b. Natural enemy movements

Fig. 1a. Experimental setup in the soybean field.

Fig. 2. Sampling design for measuring dispersal of ladybeetles between soybean and alfalfa fields, and marked lady beetles.

aphi

ds /

pot

(mea

n ±

SE)

Exclusion

Open

Field Sites

Not significant

2013

beet

les/

swee

p (m

ean

± SE

)

alf-sb sb-sbsb-alfalf-alfalf-sb sb-sbsb-alfalf-alf

2014

a

bbc

ac

a

b

abab

0.00

0

.02

0.

04

0.

06

0.0

8

0.10

0.12

0

.14

0.00

0

.02

0.

04

0.

06

0.0

8

0.10

0.12

0

.14Kruskal-Wallis chi-squared = 17.2004,

df = 3, p-value = 0.0006427

Kruskal-Wallis chi-squared = 9.6954,df = 3, p-value = 0.02134

A B

beet

les

/bott

le (m

ean

± SE

) b

alf-sb sb-alfsb-alfalf-sb

a

0.0

0.2

0.

4

0.6

0.8

1

.0

1.2

0.0

0.2

0.

4

0.6

0.8

1

.0

1.2

F = 2.6667,num df = 5,denom df = 5,p-value = 0.3055

F = 0,num df = 19,denom df = 19,p-value < 0.001

C D

Dis

tanc

e (m

) (m

ean

± SE

)

a

bb

alf-alf sb-alf sb-sb

a

b

b

ab

alf-alf alf-sb sb-alf sb-sbalf-sb

b

Kruskal-Wallis chi-squared = 14.308,df = 2,p-value < 0.001

Kruskal-Wallis chi-squared = 25.6768,df = 3, p-value < 0.001

E F

Spee

d (m

/ h

ours

) (m

ean

± SE

)

b

a

b

sb-sbalf-alf alf-alfsb-alf sb-sb alf-sb sb-alf

0

2

4

6

8 a

a

a

a

0

2

4

6

8

Movement

alf-sb

b

Kruskal-Wallis chi-squared = 11.2529,df = 2,p-value = 0.003601

Kruskal-Wallis chi-squared = 8.2845,df = 3,p-value = 0.04048G H

NS

NS

NS

*

Emigration from SBImmigration to SB

C

NS

(*)

(*)

Emigration from SBImmigration to SB

D

NSNS

NS

NS* *

Emigration from SBImmigration to SB

E

NSNS

(*)

(*)NS

*

Emigration from SBImmigration to SB

NS : Not Significant ;

* : Significant (P<0.05) ;

(*): Marginally Significant (P<0.10)

A

ALF-alfalfaCAN-canola

GRS-grasslandNV-natural vegetation

WHT-wheat

(*)

*

** NS

Emigration from SBImmigration to SB

B

Cocc-CoccinellidaeBLW-Brown lacewingsGLW-Green lacewings

NAB-NabidaeSYR-Syrphidae

aphi

ds /

pot

(mea

n ±

SE)

aphi

ds /

pot

(mea

n ±

SE)

• There was a strong suppression of soybean aphids in all field which ranged from 3- to 23-fold in 2013 and 2- to 20-fold in 2014 (Fig. 4 and 5).

• There was a significant interaction between field and treatment in 2014 due to no significant difference between open and exclusion cages in the 14LB2 field in 2014 (Fig. 4 and 5).

• We are quantifying landscape features to correlate levels of aphid suppression with landscape structure.

FactorsDf F value p-value

field 14 9.145 <0.001treatment (open vs exclusion) 1 232.035 <0.001field:treatment 14 5.303 <0.001week 1 177.32 <0.001field:week 14 6.61 <0.01treatment:week 1 0.76 0.05field:treatmet:week 14 3.16 0.31383

plot:filed:treatmentFactorsDf F value p-value

field 11 3.3 <0.001treatment (open vs exclusion) 1 175.8 <0.001field:treatment 11 1 0.414week 1 54.5 <0.001field:week 11 1.3 0.249treatment:week 1 26.8 <0.001field:treatmet:week 11 1.3 0.246

plot:filed:treatment

• There was a significant movement of ladybeetles, hoverflies, and brown and green lacewings from natural vegetation to soybean (Fig. 7B).

• There was a trend of higher number of hoverflies moving from soybean to neighbouring habitats, but the opposite was observed from natural vegetation (Fig. 7E and B).

• Hoverflies dominated natural enemies, future analysis will separate aphidophagous species from other species.

• Generalist predators exert strong suppression of soybean aphid in different agricultural landscapes in Manitoba.

• Ladybeetles can move quickly between alfalfa and soybean, tracking aphid resources.

• Natural vegetation and alfalfa act as a good sources of transient generalist predators of soybean aphid.

Future directions:

• Does the proportion of habitats in the agricultural landscape influence the diversity and abundance of transient generalist predators ?

• Does the proportion of alfalfa and natural vegetation in the landscape influence soybean aphid suppression?

• Funding agencies: Manitoba Pulse Growers Association– ARDI, NSERC Discovery, University of Manitoba.• Field Accesses: Glenlea Research Station, Carman Research Station, Owners of the commercial fields, Dennis Lange and Dr. John Gavloski • Field and Lab Assistance: Cherilyn Babel, Melanie Scallion, Diana Dunlop, Jordan Bannerman, Dave Holder, Lisa Babey, Aldo Rios, Arash Kheiroodin, Tharshi Nagalingam, Alicia Leroux, Kaitlyn Patterson, Mikala Epp, Liane Carter,

Leonardo G. da Silva and Calvin Dick.

• Costamagna, A.C. and Landis, D.A. 2006. Predators exert top-down control of soybean aphid across a gradient of agricultural management systems. Ecological Applications 16(4): 1619-1628.• Fox, T.B., Landis, D.A., Cardoso, F.F. and Difonzo, C.D. 2004. Predators suppress Aphis glycines Matsumura population growth in soybean. Environmental Entomology 33(3): 608-618.• Gardiner, M., Landis, D., Gratton, C., DiFonzo, C., O'Neal, M., Chacon, J., Wayo, M., Schmidt, N., Mueller, E. and Heimpel, G. 2009. Landscape diversity enhances biological control of an introduced crop pest in the north-central USA. Ecological Applications 19(1): 143-154.• Gavloski, J. and Bisht, V. 2014. Summary of Insects on Crops in Manitoba in 2008. [online] Available from http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/index.html [accessed 27 October 2014].• Ragsdale, D.W., Landis, D.A., Brodeur, J., Heimpel, G.E. and Desneux, N. 2011. Ecology and management of the soybean aphid in North America. Annual review of entomology 56: 375-399.• Schmidt, N. P., O'Neal, M. E., & Singer, J. W. (2007). Alfalfa living mulch advances biological control of soybean aphid. Environmental entomology, 36(2), 416-424.• Sutherland, J.P., Sullivan, M.S. and Poppy, G.M. 2001. Distribution and abundance of aphidophagous hoverflies (Diptera: Syrphidae) in wildflower patches and field margin habitats. Agricultural and forest Entomology 3(1): 57-64.• Tilmon, K. J., Hodgson, E. W., O'Neal, M. E. and Ragsdale, D. W. Biology of the Soybean Aphid, Aphis glycines (Hemiptera: Aphididae) in the United States. Journal of Integrated Pest Management 2, A1-A7, doi:10.1603/ipm10016 (2011). DOI:

http://dx.doi.org/10.1603/IPM10016• Tscharntke, T., Bommarco, R., Clough, Y., Crist, T.O., Kleijn, D., Rand, T.A., Tylianakis, J.M., Nouhuys, S.v. and Vidal, S. 2007. Conservation biological control and enemy diversity on a landscape scale. Biological control 43(3): 294-309.;• van der Werf, W., Evans, E.W. and POWELL, J. 2000. Measuring and modelling the dispersal of Coccinella septempunctata (Coleoptera: Coccinellidae) in alfalfa fields. European Journal of Entomology 97: 487-493.

Fig. 3. Bidirectional malaise trap established in the field border between soybean and the neighbouring habitat (wheat).